The objective of the proposed reserch is to develop an acoustic monitoring device for laser lithotripsy. The acoustic monitor under consideration is a fiberoptic sensor based on a novel measurement concept. In-vitro results to date have shown considerable promise for acoustic monitoring, in general, as an extremely valuable, non-visual diagnostic for laser fragmentation of urinary and biliary tract calculi. This program seeks to develop as miniaturized in-situ probe that would offer substantial clinical advantages over current-technology ultrasonic probes. The specific objectives in Phase I are to (1) determine the quantitative fiberoptic sensor response to continuous hydroacoustic waves of various frequencies and (2) determine acoustic signatures for biological materials exposed to intense laser pulses. Taken together, these objectives constitute a technical feasibility demonstration for the proposed diagnostic concept. Upon successful completion of the proposed program, a subsequent Phase II program should be initiated to provide the engineering development for a viable fiberoptic diagnostic probe and to test the probe in-vivo. A principal objective of such a program would be to develop a signal processing scheme converting the fiberoptic signal to a meaningful audible response.